utils: Add remove_ctrl

Add a helper function to remove control characters / multi-spaces, and a
test.

lib/utils/test-utils.cc

@@ -136,6 +136,22 @@ test_flatten ()
 	test_cases (cases, [](auto s, auto f){ return utf8_flatten(s); });
 }
 
+static void
+test_remove_ctrl ()
+{
+	CaseVec cases = {
+		{ "Foo\n\nbar", true,  "Foo bar" },
+		{ "",    false, "" },
+		{ "   ",    false, " " },
+		{ "Hello   World   ",    false, "Hello World " },
+		{ "Ångström", false,  "Ångström" },
+	};
+
+	test_cases (cases, [](auto s, auto f){ return remove_ctrl(s); });
+}
+
+
+
 static void
 test_clean ()
 {